JP2685284B2 - Vibration wave device - Google Patents

Description

The present invention relates to a vibration wave device such as a vibration wave motor.

[Prior Art] A vibration wave motor that produces a progressive vibration wave in an elastic body and moves a moving body such as a rotor by this vibration is small in size and can obtain high torque at a constant speed. It was used to drive the shooting lens of a reflex camera.

FIG. 6 is a vertical cross-sectional view of a photographing lens of a single-lens reflex camera in which a vibration wave motor is incorporated for driving the photographing lens. Reference numeral 1 is an annular metallic elasticity with an optical axis L of the photographing lens as a rotation center. As shown in FIG. 7, a groove 1A having a predetermined width t and depth h is provided on the entire side of the body in contact with the rotor 3 which will be described later. Further, on the lower part of the elastic body 1, two driving phases of the piezoelectric element 2 such as PZT for driving are fixed by an adhesive. Ultrasonic drive signals having different phases are respectively applied to two groups of drive phases composed of the piezoelectric elements 2 as electro-mechanical energy conversion elements by a known method, and the elastic body 1 is responsive to the signals. By vibrating, a progressive vibration wave rotating in the circumferential direction of the elastic body 1 forming the vibrating body is generated. Reference numeral 3 denotes an annular rotor having an end portion in pressure contact with the upper surface of the elastic body 1. At the other end of the rotor 3 as a moving body, an annular vibration absorber 5 such as gum is provided. Reference numeral 4 denotes an annular vibration insulator formed of felt or the like. The insulator 4 receives a pressing force from two superimposed disc springs 9 via a felt base 8.

The rotor 3 is connected to the connecting plate 22 via the vibration absorber 5 described above.
Is held closely to. The annular connecting plate 22 is fixed to the output transmission body 25 with a tightening screw (not shown). The output transmission body 25 which rotates about the optical axis L as a rotation center uses the ball 10 to form a ball bearing with ball races 13 and 14. The ball races 13 and 14 are fixed to the outer tube 12 of the taking lens, and the outer tube 1
2 is connected to the fixed barrel 11 and fixed to the camera mount 19. The connecting roller 15 is fixed to the tip of the output transmission body 25, and engages with a keyway (not shown) of the moving ring 17 holding a focus lens 27 provided in the optical axis direction. The screw portion 18a of the fixed inner cylinder 18 and the screw portion 17a of the moving ring 17 are helicoid-coupled, and the moving ring 17 can move in the optical axis direction while rotating via the connecting roller 15 by the rotational movement of the output transmission body 25. Becomes

In such a configuration, the AF signal from the camera or
A driving signal from the manual ring 16 generates a progressive vibration wave in a vibrating body composed of an elastic body and a piezoelectric element by a known method, rotates the rotor 3, and finally moves the focus lens 27 in the optical axis direction, The focus is adjusted.

In such a vibration wave motor, the vibrating body has the same driving progressive vibration wave at any position on the vibrating body,
It is formed of a uniform member so as to have the same wavelength, and has a substantially uniform structure as shown in FIG.

[Problems to be Solved by the Invention] However, noise may occur in the conventional vibration wave motor described above.

An object of the present invention is to provide an oscillating wave device that does not cause noise by preventing the generation of a traveling wave of an unnecessary wavelength without affecting the wavelength of the drive mode.

[Means for Solving the Problem] A configuration for achieving the object of the present invention is provided with an electro-mechanical energy conversion means having a positional phase difference, and excites a plurality of standing waves whose positional phases are mutually displaced. In a vibration wave device having an elastic body forming a progressive vibration wave for driving,
A plurality of grooves are formed in the elastic body at substantially equal pitches to change the dynamic rigidity at the groove position, and the elastic body or other members of the vibration wave device to which the vibration wave of the elastic body is transmitted are , Seeing in a vibration mode that vibrates in an order different from the driving vibration mode excited in the elastic body by the electro-mechanical energy conversion means, the dynamic rigidity at a position of an integer multiple or approximately an integer multiple of the half wavelength thereof, Further, the symmetry plane at each position where the dynamic rigidity is changed and the symmetry plane of the dynamic rigidity of the electro-mechanical energy converting means are made to coincide or substantially coincide with each other.

[Operation] In the above-mentioned configuration, for example, when an elastic body is taken as an example,
When the groove depth is changed as a means for changing the dynamic rigidity at a position of an integral multiple or about an integral multiple of a half wavelength as compared with the dynamic rigidity at other positions, a driving vibration mode excited in the elastic body When the order of is 7 waves, for example, by forming a groove at an integer multiple or approximately an integer multiple of a half wavelength of a vibration mode of 6 waves deeper than a groove at other positions, a vibration mode of 6 waves can be obtained. The natural frequencies of the one standing wave and the other standing wave are different, and the squeaking can be prevented. At that time, the symmetry planes of the respective positions where the dynamic rigidity of the elastic body is changed (dynamic rigidity change positions formed by other than a plurality of grooves of substantially equal pitch) and the dynamic rigidity of the electric-mechanical energy conversion means are symmetrical. By matching or substantially matching the surface, the driving vibration mode is prevented from being affected by the change in dynamic rigidity.

[Embodiment] FIG. 1 is a plan view of an elastic body showing an embodiment of a vibration wave motor as a vibration wave device of the present invention.

The elastic body 28 according to this embodiment is formed in an annular shape as shown in FIG. 7, and has a plurality of grooves formed on the pressure contact surface side of the moving body (not shown) in order to increase the amplitude.

In this embodiment, 90 grooves are formed at a pitch of 4 °, and in addition to the purpose of expanding the amplitude described above, in order to prevent the generation of traveling waves in unnecessary modes, the grooves are blacked out in the figure. 28b, 28c, 28d, 28e, 28f, 28g, 28h, 28i, 28k, 28l, 28
The depth h of the 14 grooves of m, 28n, and 28o (hereinafter referred to as deep grooves) is made slightly deeper than the other grooves 28a (total of 76 grooves) by, for example, 0.2 mm to change the dynamic rigidity. In addition, the vibrating body of the present embodiment is configured so that the drive mode is the 7th mode (7-wave mode) of the out-of-plane bending vibration.

Therefore, the squeal that occurs when the motor is driven is in the 3rd, 4th, 5th, and 6th (wave) because it is a lower-order mode than the drive mode.
Either of the modes, or a combination thereof, will occur. In the motor shown in the conventional example, the secondary mode was hardly generated, probably because it was unstable considering the contact state between the elastic body and the moving body.

Prevention of squealing will be described below, taking as an example a case where an unnecessary mode of the fifth order mode occurs in the vibration wave motor having the elastic body 28 having such a structure with non-uniform dynamic rigidity.

The principle of forming a progressive vibration wave is that the wavelength (λ) is equal to the frequency and the positional phase is shifted by λ / 4 or two standing waves are combined. Therefore, in order to prevent the generation of the traveling wave of the unnecessary mode, it is sufficient that the natural frequencies of the two standing waves in the unnecessary mode formed on the elastic body 28 do not become equal. Therefore, in this embodiment, The deep grooves 28b ... 28h ... 28o are formed to form the elastic body 28.
The non-uniformity of the dynamic rigidity is achieved.

In the formation of a traveling wave, the two standing waves are out of phase with each other by λ / 4. This means that if there is an antinode of one of the standing waves at an arbitrary point in the circumferential direction of the elastic body 28, There must be another standing wave node.

In the vibration wave of the fifth mode, one wavelength formed on the elastic body 28 has a pitch of 72 °. If five standing waves with the deep groove 28b as a node are generated, the deep waves 28e, 28h, 28i, 28j, and 28m are located in antinodes, and the elastic waves corresponding to the standing waves are present. The natural oscillator of the body 28 is f _rc . Also,
If five standing waves with the deep groove 28b as an antinode are generated,
The standing waves have nodes at the deep grooves 28e, 28h, 28i, 28j, and 28m, and the natural frequency of the elastic body 28 corresponding to the standing waves is represented by f _rs
And

A traveling wave of the fifth order mode is generated, the natural frequency f _rs and f _rc and is equal to or characteristic frequency difference of both the standing _{wave, Δf r5 = | f rs -f} rc | is small Is required, and conversely, if the natural frequency difference Δf _r5 is large, the fifth-order mode traveling wave is not generated.

In general, natural frequency f _r where mass is m and rigidity is k
Is The bending rigidity k is small in the deep groove portion because the elastic plate is thin. Thus the flexural rigidity of the case of the belly position of the deep groove and k _c, the bending rigidity and k _s in the case of a node position of the deep groove, the thickness of the loop position at which a node position of the deep groove is thick Therefore, k _s > k _c, that is, f _rs > f _rc .

Accordingly, different frequency from the natural frequency f _rs and f _rc in the following mode, since the difference is large, the frequency of the fifth-order modes that may occur in the squeal not obtained becomes traveling wave, the fifth-order mode Even if the frequency of is generated for some reason, the squeal does not occur.

The effect of preventing this squeal is due to the natural frequency difference Δf.
Obviously, the larger _r5 is, the more remarkable it is.

The above invention is the case where the unnecessary mode is the fifth mode, but in the elastic body 28 of the present embodiment, not only the fifth mode but also the unnecessary modes such as the sixth mode, the fourth mode, and the third mode. As in the case of the fifth-order mode, the formation of traveling waves is blocked.

That is, in the case of the fourth mode, the deep grooves 28b, 28f, 28g, 28i,
28k, 28l is a dynamic rigidity non-uniform, to prevent the formation of a traveling wave of 4-order modes with different natural frequencies difference Delta] f _r4 at the position of the vibration wave.

However, in this case, since the grooves formed on the elastic body 28 and having a uniform pitch of 90 perimeter are not divisible by 4, the deep groove 28
The middle position of f, 28g, (same for 28k, 28l) is set as the center position, and the pitch is 90 °, which is one wavelength of the fourth mode.

In addition, in the case of the third mode and the sixth mode, the deep grooves 28c, 28
d, 28f, 28g, 28k, 28l, 28n, 28o is a dynamic stiffness uneven, tertiary varied natural frequency difference Delta] f _r3, a Delta] f _r6 at the position of the vibration wave, traveling wave formed in the sixth-order mode Prevent.

However, also in this case, the deep grooves 28c, 28d, the deep grooves 28f, 28g,
Centering the middle of the deep grooves 28k, 28l and the deep grooves 28n, 28o, 1/2 wavelength in the 3rd mode, 1 in the 6th mode
The pitch is 60 °, which is the wavelength.

FIG. 3 shows the natural frequency difference Δf _{rn of} these nth modes.
Is obtained for each mode.

As can be seen from FIG. 3, the 7th mode for driving also has a natural frequency difference Δf _r7 due to the nonuniform dynamic rigidity, but the amount is small. Moreover, it is generated during other noises. 3
Natural frequency difference Δf _r3 , Δf of the 4th, 5th and 6th modes
_{Since r4} , Δf _r5 , and Δf _r6 are larger than Δf _{r7 in} the case of the 7th mode, it can be seen that the squeal prevention effect is greater. That is, the motor drive is unlikely to be adversely affected, and squeal is unlikely to occur.

That is, the natural frequency difference Δf of each of these modes
_rn greatly depends on the deep groove pattern as shown in FIG. 1, that is, the dynamic rigidity nonuniform portion pattern.

FIG. 2 is a plan view of the piezoelectric element 30 of this embodiment. That is, it is a view of the piezoelectric element 30 bonded to the elastic body 28 of FIG. 1 as viewed from the back surface side. Electrode group shown by 30A is the A-phase driving electrodes, and has a collection of wavelength lambda ₇ of lambda _7/2 electrodes of the 7-wave drive. In the figure, + and − of the applied voltage at the time of polarization processing to the common electrode (not shown) formed on the back surface are shown. Electrode group shown in 30B is in the B-phase driving electrode group, lambda _7/4 phase to the A phase driving electrodes are formed on the displacement or position.
The A-phase drive electrode 30A and the B-phase drive electrode 30B are line-symmetric with respect to the symmetry plane 31. A-phase drive electrode when driving the motor
An alternating voltage having a phase difference of ± 90 ° with respect to time is applied to the 30A and B-phase drive electrodes 30B.

FIG. 4 shows that the vibration wave of the nth mode in the θ direction from the symmetry plane 29 of the elastic body 28 shown in FIG. 1 corresponds to one wavelength of each mode (φ _n =
It is a figure which calculated the substantial total R of the dynamic-stiffness nonuniformity part (deep groove of FIG. 1 black color) at the time of advancing (360 degree). That is, θ = θ _n / n. 32,33,34,35 are the third and fourth respectively
This is the case of vibration modes that generate noise such as the next, fifth, and sixth modes. As shown in FIG. 4, each mode has the maximum and minimum values of R at the positions where the phase φ _n is shifted by about 90 °. In other words, the non-uniformity of dynamic rigidity is about 90 ° out of phase
It is the smallest and has the shape that is most unlikely to be a traveling wave.
FIG. 5 is a view similar to FIG. 4, but for the seventh driving mode 36. From this figure, it can be seen that the maximum and minimum differences in R are smaller than in other modes. That is, there is little adverse effect on the traveling wave in the 7th mode. However, it is not zero. Elastic body now
When the symmetry plane 29 of the deep groove pattern 28 and the symmetry plane 31 of the piezoelectric element 30 are aligned, the antinode position of the A-phase standing wave when P ₁ and P ₃ drive only the A-phase 30A (only the B-phase 30B) B when driving
The node position of the phase standing wave), P ₂ and P ₄ are the antinode positions of the B phase standing wave (A
Node position of the standing wave). Since the R values of P _{1 to} P ₄ are equal, it can be seen that the nonuniformity of the dynamic rigidity has a similar effect on the drive electrodes of the A phase and the B phase. That is, the natural frequency of the A-phase standing wave and the natural frequency of the B-phase standing wave match each other, and the driving is not adversely affected. However, the symmetrical surface 29 of the deep groove pattern of the elastic body 28 and the symmetrical surface 31 of the piezoelectric element 30 are displaced from each other. , P ₅ (P ₉ ) and P ₇ are antinode positions of the A phase standing wave (node positions of the B phase standing wave), and P ₆ and P ₈ are antinode positions of the B phase standing wave (A phase). The node position of the standing wave) or vice versa.

In this case, the R value of P ₅ (P ₉ ) and P ₇ is larger than the R value of P ₆ and P ₈ . In other words, due to the non-uniformity of dynamic rigidity, A
The natural frequency of the B-phase standing wave becomes higher than the natural frequency of the phase standing wave, and the unevenness as a traveling wave becomes large. From this, the symmetry plane 29 of the elastic body 28 and the symmetry plane 31 of the piezoelectric element
It can be seen that matching the values does not adversely affect the drive wave.

In addition, the substantial sum R of the above-mentioned non-uniform dynamic rigidity is
Assuming that one size of the dynamic stiffness non-uniformity is R _oi , the shape of bending vibration is approximated by S _in , and considering the total sum over the entire elastic ring, Becomes However, k is the number of portions with non-uniform dynamic rigidity.

If the dynamic rigidity non-uniformity portion is a deep groove as in this embodiment, R (φ _n ) represents the distribution of the total sum of the deep groove depending on the traveling wave position (φ _n ). 4 and 5 show R _oi = 1
Is the case. In the case of this embodiment, as described above, the smaller the antinode of vibration is, the smaller the k becomes. That is, f _{r is} small. Therefore, the natural vibration plate of the mode serving as the antinode of vibration is minimized at the maximum position of R, and the natural frequency of the mode serving as the antinode of vibration is maximized at the minimum position of R.
In fact, the traveling wave that becomes noise takes a frequency between this maximum and minimum natural frequency. Therefore, the larger the difference in their natural frequencies is, the more the signal wave that becomes noise deviates from the resonance point, the amplitude becomes extremely small, and the more it is attenuated.

In the above-mentioned embodiments, the deep groove is described as being deeper than the other grooves by 0.2 mm. However, it is clear that increasing the amount will increase the effect, and the present invention is not limited to this value.

Further, not only changing the depth of the groove in this way, but also changing the dynamic rigidity by increasing or decreasing the additional mass or the additional resistance, or changing the dynamic rigidity by combining them is also the same. Further, not only the dynamic rigidity of the elastic body but also the dynamic rigidity of peripheral members such as the rotor and the vibration insulator 4 shown in FIG. Furthermore, the non-uniform dynamic rigidity pattern is not limited to that of the present embodiment, and may be any pattern in which the dynamic rigid bodies are made equal or close to each drive phase.

[Effects of the Invention] As described above, according to the present invention, it is possible to provide a dynamic rigidity non-uniform portion in an elastic body, for example, without using an electric control unit such as an electric circuit. It is possible to prevent the formation of the traveling wave of No. 1 and to suppress the noise such as squeaking at the time of driving, and to obtain the effect that it does not affect the formation of the traveling wave for driving.

[Brief description of the drawings]

FIG. 1 is a plan view of an elastic body showing a first embodiment of a vibration wave motor as a vibration wave device of the present invention, FIG. 2 is a plan view showing the arrangement of piezoelectric elements, and FIG. Figures showing the difference in natural frequency of each mode for each mode, Figures 4 and 5 show changes in dynamic rigidity depending on the phase of the nth mode, and Figure 6 is a sectional view of the lens barrel. FIG. 7 is a perspective view of the elastic body. 1,28: Elastic body 2,30: Piezoelectric element 3: Rotor 4: Vibration insulator 28b… 28i… 28o: Deep groove

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akio Atsuta 770 Shimonoge, Takano-ku, Kawasaki-shi, Kanagawa Kanagawa Plant, Canon Inc. In-house (72) Inventor Hiroshi Ueda 770 Shimonoge, Takatsu-ku, Kawasaki-shi, Kanagawa Canon Inc. Tamagawa Plant

Claims (1)

(57) [Claims] 1. A vibration having an elastic body which is provided with an electro-mechanical energy converting means having a positional phase difference and which excites a plurality of standing waves whose positional phases are shifted from each other to form a progressive vibration wave for driving. In the wave device, a plurality of grooves are formed in the elastic body at substantially equal pitches to change the dynamic rigidity at the groove positions, and the elastic wave of the elastic body or the elastic body is transmitted. The other member is viewed at a vibration mode that vibrates in an order different from the driving vibration mode excited in the elastic body by the electro-mechanical energy conversion means, and at a position of an integral multiple or an approximately integral multiple of its half wavelength. The oscillating wave is characterized in that the kinematic rigidity of the electric-mechanical energy conversion means and the symmetry surface of each position where the kinetic rigidity of the electric-mechanical energy converting means are made to coincide or substantially coincide with each other. apparatus.